1. Field of the Invention
The present invention relates to a planar light source of side light type in which lamps are arranged along side faces of a light guide plate, and particularly to a planar light source of side light type in which a plurality of lamps are arranged and a display device having the planar light source.
2. Description of the Related Art
In order to realize a high-brightness display device, there is recently disclosed a technique for enhancing the brightness of a planar display device disposed behind a display element by means of increasing the number of lamps.
In a backlight device described in JP-A-6-230229 (pp. 2 to 3, FIGS. 2 through 4), a light source 1 is placed in a number of three along each of mutually-opposing two sides of a light guide plate 4, thereby achieving high brightness. However, the light sources 1 are arranged in an overlapping manner, and the luminous efficiency of the light sources 1 is deteriorated by influence of the heat developing from the light sources 1, to thus raise a problem of a failure to achieve enhanced brightness.
In a planar light source described in JP-A-9-259625 (pp. 2 to 7, FIGS. 1 and 2), lamps 1 are fixed by means of a lamp reflector 3 by way of a rubber holder 2, thereby keeping the lamps 1 spaced apart from each other at a predetermined interval so as not to contact each other.
In a backlight device described in JP-A-2003-197018 (pp. 4 to 9, FIGS. 6 through 8), when a plurality of fluorescent tubes 23 are placed, the center fluorescent tube 23 becomes most heated. For this reason, the center fluorescent tube 23 is displaced in proximity to a holder 27, thereby realizing a structure for efficiently transferring heat to the holder 27. However, such a structure encounters a problem of variations in the longevities of the respective fluorescent tubes 27 as well as a problem of occurrence of variations in leakage currents from the fluorescent tubes 23 and a failure to attain brightness proportional to the number of tubes.